A case study of Chlorophyll a response to tropical cyclone Wind Pump considering Kuroshio invasion and air-sea heat exchange

• Published in: The Science of the total environment Vol. 741; p. 140290
• Main Authors: Liu, Yupeng, Tang, Danling, Tang, Shilin, Morozov, Evgeny, Liang, Wenzhao, Sui, Yi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2020
• Subjects: case studies; chlorophyll; Chlorophyll a concentration; cooling; environment; Gulf Stream; Heat flux; heat transfer; hurricanes; Kuroshio; Mesoscale eddy; nutrient uptake; oceans; Philippines; remote sensing; South China Sea; Tropical cyclone; Wind Pump; South China Sea; Wind Pump; Kuroshio; Chlorophyll a concentration; Tropical cyclone; Heat flux; Mesoscale eddy
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.140290

New evidences provided that the tropical cyclone (TC) Linfa in 2015 induced looping path of Kuroshio invasion into the northeastern South China Sea (NESCS) through the northwestern Luzon Strait (LS), based on the in-situ measurements, satellite data and model output data. This TC-enhanced Kuroshio invasion with low nutrients and denser waters suppressed the TC “Wind Pump” induced upwelling and nutrients uptake, and therefore inhibited the Chlorophyll a concentration (Chl-a) increase from surface to ~50 m in the open ocean of the NESCS. The TC-induced Kuroshio invasion promoted the generation of the strong cyclonic eddy to its left side where weak Ekman Pumping Velocity was observed. This enhancing cyclonic eddy then dominated the nutrients uplift and increased the surface and subsurface (0–50 m) Chl-a through eddy pumping rather than Ekman Pumping. The TC-declined anti-cyclonic eddy, which shoaled the Mixed Layer Depth (MLD), benefited to the nutrient uptake through TC-induced upwelling and thereby increased the surface Chl-a and raised the Chl-a Maximum Layer (CML) to ~20 m over the southwestern LS. The temporal Chl-a variations were also influenced by TC intensities and biochemical processes. The air-sea heat budget analysis indicated that, the air-sea heat exchange contributed to nearly 80% of the sea surface cooling (SST cooling) over the northwestern LS with Kuroshio invasion, while eddy-induced upwelling dominated the SST cooling over the western LS, and the wind-driven upwelling (and mixing) controlled the SST cooling over the southwestern LS. These different formations of SST cooling then played important role in Chl-a variations. This study is the first case of TC “Wind Pump” induced Chl-a variations considering air-sea heat exchange, Kuroshio invasion and mesoscale eddies over LS, which would help to evaluate the influence of TCs over the other major heat transport arteries of the world ocean: The Gulf Stream area. [Display omitted] •TC “Wind Pump” enhanced Kuroshio invasion which then inhibited the surface Chl-a.•Eddy-induced upwelling dominated Chl-a increase rather than wind-driven upwelling.•TC-enhanced Kuroshio invasion reduced a cyclonic eddy which right on its way.•TC-enhanced Kuroshio conduced to a cyclonic eddy generation in its left side.•Air-sea heat exchange dominated SST cooling which then inhibited Chl-a increase.